<div ng-controller="TestController">
    <input ng-model="a" type="text"></input> +
    <input ng-model="b" type="text"></input> <button class="btn" ng-click="add(a,b)"> = </button>
    {{sum}}
    <p>
        <div ng-bind-html="htmlString"></div>
    </p>

    {{data}}
</div>